Backlights are used as extended area illumination sources in displays such as liquid crystal displays (LCDs). Backlights typically include one or more lamps, a lightguide for producing an extended area light source by extending light from the lamps over the output surface of the backlight, and one or more light management layers such as prismatic light redirecting layers, brightness enhancement layers, reflective polarizer layers, diffuser layers, mirror layers and retarder layers.
Light propagating in a lightguide is typically extracted by light extraction features provided on a major surface, such as the output surface, of the lightguide.